Logging devices which measure formation dielectric constant are known, for example from U.S. Pat. No. 3,849,721 and U.S. Pat. No. 3,944,910. The logging device includes a transmitter and spaced receivers mounted in a pad that is urged against a bore hole wall. An electromagnetic microwave is transmitted into the formations, and the wave which has propagated through the formations is received at the receiving antennas. The phase shift and attenuation of this wave propagating in the formations is determined from the receivers output signals. The dielectric constant and the conductivity of the formations can then be obtained from the phase shift and attenuation measurements. Two transmitters are generally used in a bore hole compensated array to minimize the effect of bore hole rugosity, tool tilt, and dissimilarities in the transmitters, receivers, and their electronic circuits.